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Conservation challenge: Our depleted oceans – what lies beneath…

depleted-oceans
Written by: Dr Abigail Entwistle
Other posts by Dr Abigail Entwistle

We think of our oceans – the lifeblood of this blue planet – as a vast and unknown wilderness.

However, if you peek beneath the waves the oceans are no longer pristine. Instead the evidence of man’s impact on oceans and their life is immediately obvious. From the bleached corals to the floating litter, from the decimated fish populations to ravaged seabeds, mankind’s impacts are reaching wider and deeper into our marine environment.

A key biodiversity issue…

As rapidly as we are learning about the biodiversity of our seas, marine species are being placed at risk of extinction.

Species that once were a staple of commercial fisheries (such as cod and bluefin tuna) are now threatened. A range of other species (such as albatrosses, dolphins and turtles) are at risk as a result of their accidental capture by fisheries. Marine habitats are also being destroyed – be it by heavy bottom trawling equipment ploughing up the sea bed, or dynamite fishing destroying the very reefs where the fish breed.

Fishing is not the only issue – marine species and habitats are being destroyed by poorly planned coastal development, a changing climate and by pollution.

Pollution can range from very dramatic incidents (such as the Deepwater oil spill in 2010 with its immediate impacts on local wildlife) to more insidious sources of pollution such as the agricultural run off that causes algal blooms offshore.

There is now evidence that even tiny particles of plastic are causing damage – by accumulating toxic pollutants into the foodchain.

… and more

The damage to our oceans is not just an issue in terms of lost biodiversity. It also has implications in terms of global food security, loss of cultural heritage and – potentially – changes to key planetary processes.

Declining fisheries

Many commercial fish species are significantly over-fished – resulting in species declines and knock-on effects for other creatures in the wider food web. A recent study in Science suggested that the world’s commercial fisheries could collapse by 2050.

Loss of fisheries would have significant consequences, not just for the traditional livelihoods of fishermen, but for all those coastal communities relying on fish as a key source of protein.

Inefficient fisheries

The practice of discarding healthy fish has recently been highlighted in the media. Less well known is that over a third of all fish caught is not for direct human consumption but is for conversion into fishmeal – for use in fish farms and increasingly in agricultural production as both poultry and pig feed.

Damaged reefs

The world’s coral reefs are under threat from a condition known as coral bleaching which occurs when coral lose their symbiotic algae (zooxanthellae). Coral provides zooxanthellae with a protected environment and compounds it needs in order to photosynthesise and in return the zooxanthellae supply the coral with organic products from photosynthesis which are used by the coral to grow. One of the by-products of this symbiotic relationship is the beautiful and vibrant colours we see on live coral.

But this relationship is fragile, and when the conditions needed to sustain zooxanthellae can no longer be met the algae is expelled by the coral, resulting in the loss of this vivid colour – hence coral bleaching. Rising sea temperatures (as a result of human-induced climate change) is one of the primary causes of coral bleaching worldwide.

Loss of coral reefs directly affects fisheries (as many fish species depend on these structures), but also affects the economies of those countries reliant on dive tourism.

Changes to climate regulation

At present oceans provide an important buffer to global temperature increases and are also an important sink for atmospheric CO2 – a process primarily governed by microscopic organisms called plankton.

However, it is not clear how increasing temperatures, and wider changes to marine ecosystems, might affect the ability of plankton to continue to absorb CO2. At the same time other ocean habitats that store carbon dioxide (such as coastal mangrove forests and submerged seagrass beds) are also being destroyed.

The need to act

The need for improved marine conservation is both clear and urgent.

  • In the short term we need to place more of the ocean under protection, to enable marine habitats and species to recover. Currently only 1% of the marine environment is formally protected – there is a need to see at least 10% protected – and ideally an area of over 25%.
  • There needs to be better planning and management of fisheries to ensure that key species survive and that the fisheries can be commercially sustainable.
  • Pollution of the marine environment needs to be better regulated, and more attention needs to be given to the issue of plastics in our seas.
  • We need to better understand how increased CO2 in the atmosphere will affect out oceans – be it as a result of increased acidity of the oceans or global climate change.
Written by
Dr Abigail Entwistle

Abi joined FFI in 1996 after studying Zoology at Oxford University and completing a PhD in bat ecology at Aberdeen University. Since then she has held a number of roles in the organisation, and is currently Director of Conservation Science.

Other posts by Dr Abigail Entwistle

“From the bleached corals to the floating litter, from the decimated fish populations to ravaged seabeds, mankind’s impacts are reaching wider and deeper into our marine environment.”

Dr Abigail Entwistle

Director of Conservation Science

We think of our oceans – the lifeblood of this blue planet – as a vast and unknown wilderness. However, if you peek beneath the waves the oceans are no longer pristine. Instead the evidence of man’s impact on oceans and their life is immediately obvious. From the bleached corals to the floating litter, from the decimated fish populations to ravaged seabeds, mankind’s impacts are reaching wider and deeper into our marine environment.

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